We refer to the Sandia report SAND-2004-2188 for a detailed overview of Amesos. A PDF version of this report can be found the Trilinos/packages/amesos/doc/AmesosReferenceGuide/AmesosReferenceGuide.pdf.

Copyright and licensing of the third party codes

Most of the Amesos classes are based on a third party code (that is, not distributed within Trilinos). Each third party code comes with its own copyright and/or licensing requirements. It is responsibility of the user to fulfill the requirements of each supported package' copyright.

Most of these third party codes are intended to be made available at no cost to users. Much of the copyright and licensing restrictions concern rights to modify, redistribute the code and generally include a request that credit be given in any papers which make use of their code. Please refer to the web page for the package that you are interested in for details.

(*) MUMPS required FORTRAN communicators. Some architectures (e.g., SGI) does not allow portable conversions from C/C++ communicator and FORTRAN. On these architectures, therefore, MPI_COMM_WORLD will be used by MUMPS. Instead, if C/C++ communicators can be converted to FORTRAN ones, then any number of prosesses can be used by Amesos_Mumps.

(**) DSCPACK requires a number of processes that is a power of 2.

Supported Matrix Formats.

The following table details the supported matrix formats for each class.

Installing Amesos

Each of the Amesos classes provides an interface to a third party direct sparse solver code. (Exception is KLU, whose sources are distributed within Amesos.) In order to install a particular class, you must first install the underlying direct sparse solver code.

As all other Trilinos packages, Amesos is configured and built using the GNU autoconf and automake tools. To configure Amesos from the Trilinos top directory, a possible procedure is as follows. Let TRILINOS_HOME be a shell variable representing the location of the Trilinos source directory, and % the shell prompt sign. Let us suppose that we want to configure Amesos on a LINUX machine with MPI, with support for KLU and UMFPACK. Header files for UMFPACK are located in directory /usr/local/umfpack/include, while the library, called libumfpack.a is located in /usr/local/umfpack/lib. The configure like will look like:

% cd $TRILINOS_HOME

% mkdir LINUX_MPI

% cd LINUX_MPI

% ../configure \

--with-mpi-compilers \

--prefix=$TRILINOS_HOME/LINUX_MPI \

--enable-amesos \

--enable-amesos-klu \

--enable-amesos-umfpack \

--with-incdirs="-I/usr/local/umfpack/include" \

--with-ldflags="-L/usr/local/umfpack/lib" \

--with-libs="-lumfpack"

% make

% make install

Other flags may be required depending on the location of MPI, BLAS and LAPACK. The table below reports the architectures and compilers tested with each of the Amesos classes. "nightly" means that these tests are included in out routine (though not always nightly) testing. "yes" means that theses tests were run at least once.

This table may soon be replaced by a table which reports only the results of the routine, "nightly", tests. MANUAL TESTING will continue to list of architectures and compilers on which Amesos solvers have been tested manually.

Example of Use of Amesos Classes

Note that these header files will not include the header files for the supported libraries (which are of course needed to compile the Amesos library itself). Now, let define the linear system matrix, the vector that will contain the solution, and the right-hand side as:

It is important to note that all available solvers can be selected simply by changing an input parameter. Some solvers are serial, other parallel; generally, each solver has its own matrix format. However, the user will still have the same interface to all of them.

The Factory object will create an Amesos_Klu object (if Amesos has been configure to support this solver). Factory.Create() returns 0 if the requested solver is not available. Parameter names are case-sensitive; misspelled parameters will not be recognized. Method Factory.Query() can be used to query the factory about the availability of a given solver:

Here, ParameterName is a string containing the parameter name, and ParameterValue is any valid C++ object that specifies the parameter value (for instance, an integer, a pointer to an array or to an object). Please consult the Amesos Reference Guide for more details. The Doxygen documentation of each class can also be of help.

Note that Problem is still empty. After setting the pointer to the linear system matrix, we can perform the symbolic factorization of the linear system matrix:

(AMESOS_CHK_ERR is a macro, that checks the return error and, if not null, prints out a message and returns.) This phase does not require the numerical values of A, that can therefore be changed after the call to SymbolicFactorization(). However, the nonzero pattern of Acannot be changed.

Should the user need to re-factorize the matrix, he or she must call NumericFactorization(). If the structure of the matrix is changed, he or she must call SymbolicFactorization(). However, it is supposed that the linear system matrix and the solution and right-hand side vectors are still defined with the same Epetra_Map.

Please consult the examples reported in the amesos/example subdirectory: